In 2020, four artificial reefs were installed in the Borssele 1&2 wind farm. The reefs consist of 45 concrete pipes of different sizes. More than sixty cod were caught from the reefs and equipped with acoustic transmitters. In addition, sixteen receivers were installed around the artificial reefs to “hear” and track tagged cod. The data from the transmitters provided detailed information on the movement and behavior of the tagged cod.
The results show that most fish stayed near the reefs for a long time. The researchers also saw that the cod spent a lot of time in and around the concrete pipes. This gives the impression that these structures play an important role as foraging areas and shelters.
Biodiversity in offshore wind farms (Source: Wageningen Marine Research)
Artificial reefs more attractive than traditional erosion protection
This research offers valuable insights into the nature-inclusive construction of wind farms and the creation of a suitable habitat for North Sea species. Artificial reefs attracted cod better than erosion protection with rocks around monopiles. Artificial reef tubes provide much larger openings that provide shelter for cod. Two of the four artificial reefs were installed on a rock layer and two directly on the sandy seabed. Both models attracted cod equally.
The return of reefs: a way to promote the recovery of North Sea species?
Wind farms can have a negative impact on marine life during construction and operation, for example due to underwater noise – especially during piling foundations -, electromagnetic fields around power cables and habitat degradation. According to Benoît Bergès, lead scientist and marine scientist at Wageningen Marine Research, a positive contribution has the potential to create suitable habitats for some North Sea species. “I’m really looking forward to studying the food availability and energy expenditure of fish around artificial reefs and finding out if these reef structures actually lead to increased fish production, which ultimately benefits the fish population.”
Borssele 1&2 wind farm
After the construction of the Borssele 1&2 wind farm in 2020, four artificial reefs were installed around one monopole of the wind farm. Following this deployment, Ørsted and Wageningen University & Research implemented a cod monitoring program in 2021 and 2022 to study the use of artificial reefs and the behavior of the animals around them.
More information
Text: Benoît Bergès and Cecile Leuverink, Wageningen Marine Research; Bregje van Rij, Orsted
Photo: Peter Verhoog (Cod near the reef)
Video: Wageningen Marine Research